JP3860820B2 - Method for producing 3,3 ', 5,5'-tetraalkyl-4,4'-biphenol - Google Patents

Description

  The present invention relates to a process for producing 3,3 ′, 5,5 ″ -tetraalkyl-4,4′-biphenol, and more specifically, 3,3 ′, 5,5 by oxidation dimerization of 2,6-dialkylphenol. When producing 5′-tetraalkyl-4,4′-biphenol, industrially advantageous 3,3 ′, 5,5′-tetraalkyl-4, which is obtained by collecting and reusing unreacted raw materials, The present invention relates to a method for producing 4′-biphenol. Hereinafter, 3,3 ′, 5,5′-tetraalkyl-4,4′-biphenol may be abbreviated as “tetraalkylbiphenol” in some cases.

  Tetraalkylbiphenol is a useful compound as a raw material for epoxy resins, polyester resins, polycarbonate resins, etc., and as a raw material for stabilizers and plasticizers for petroleum products. Among them, tetraalkylbiphenol whose alkyl group is a methyl group is useful in the electrical and electronic fields as a raw material for epoxy resins.

  As a method for synthesizing a tetraalkylbiphenol, a method is known in which 2,6-dialkylphenol (hereinafter sometimes abbreviated as “dialkylphenol”) is oxidized and dimerized in an aqueous solvent in the presence of a metal catalyst and an oxidizing agent. Thus, tetraalkylbiphenol can be obtained with a relatively high yield (see, for example, Patent Documents 1 and 2). Specifically, this method includes (1) a step of performing an oxidative dimerization reaction of 2,6-dialkylphenol with oxygen or an oxygen-containing gas in the presence of a water solvent and a metal catalyst, and (2) the reaction obtained And solid-liquid separation of the tetraalkylbiphenol from the mixture (aqueous slurry).

  When the tetraalkylbiphenol is industrially produced by the above method, a particularly preferred treatment method has been conventionally known for the treatment of the reaction solution containing the unreacted raw material dialkylphenol after the oxidation dimerization reaction and the solid-liquid separation. The fact is that it is not. For example, it is known that the reaction liquid can be heated and azeotropically distilled with water and dialkylphenol (see, for example, Patent Documents 3 to 4), but the mixture of distilled and recovered water and dialkylphenol is reused. Not known about what to do. Therefore, it is common to dispose of unreacted 2,6-dialkylphenol after the reaction, but the product cost increases due to the disposal of unreacted raw materials and the cost of disposal, and a large amount of reaction. The disposal of the liquid is not preferable from the viewpoint of the global environment. Therefore, it is very important industrially to recover and reuse the dialkylphenol in the reaction solution.

The present inventors distilled and recovered the above azeotrope composed of water and dialkylphenol and tried to reuse it as a part of the raw material as it was, but as the recovery and reuse were repeated, the oxidation dimerization reaction A problem was encountered in that the reaction time to a predetermined conversion rate gradually increased.
JP-A-53-65834 JP 60-152433 A JP-A-61-268641 Japanese Patent No. 2861221

  The present invention has been made in view of the above circumstances, and the problem to be solved is that even if the unreacted dialkylphenol is recovered and reused repeatedly, the conversion rate in the oxidation dimerization reaction is reduced and the reaction time is reduced. An object of the present invention is to provide an industrially advantageous production method in which the increase is suppressed and the amount of discarded reaction solution can be reduced.

  As a result of intensive studies in view of the above problems, the inventor of the present invention (1) that the increase in the reaction time is due to the reactivity-inhibiting action due to the accumulation of 2-carbonylphenol compounds by-produced as impurities, 2) A mixture containing water, unreacted 2,6-dialkylphenol and 2-carbonylphenol compound as impurities is recovered by distilling from the reaction liquid after the oxidation dimerization reaction and / or after the solid-liquid separation, It has been found that by supplying a part of the fraction to the oxidation dimerization reaction, the accumulation of impurities is suppressed, and the present invention has been completed.

The first gist of the present invention is to carry out an oxidative dimerization reaction of 2,6-dialkylphenol with oxygen or an oxygen-containing gas in the presence of a water solvent and a metal catalyst, and to convert unreacted 2,6-dialkylphenol and the metal catalyst. A step (A) of obtaining an aqueous slurry in which 3,3 ′, 5,5′-tetraalkyl-4,4′-biphenol is dispersed in the aqueous reaction solution to be contained, and 3,3 ′, 5 from the obtained aqueous slurry , 5′-tetraalkyl-4,4′-biphenol comprising a step (B) of solid-liquid separation, and a method for producing 3,3 ′, 5,5′-tetraalkyl-4,4′-biphenol The aqueous slurry is distilled by a rectification method after the step (A) and before the step (B), and is represented by the following general formula (I) as water, unreacted 2,6-dialkylphenol and impurities. 2-carbonylpheno 3,3 ′, 5,5′-tetraalkyl-4, characterized in that a mixture containing a disulfide compound is distilled and recovered, and a part of the recovered fraction is supplied to an oxidative dimerization reaction. It exists in the manufacturing method of 4'-biphenol.

The second gist of the present invention is to carry out an oxidative dimerization reaction of 2,6-dialkylphenol with oxygen or an oxygen-containing gas in the presence of a water solvent and a metal catalyst, and to convert unreacted 2,6-dialkylphenol and the metal catalyst. A step (A) of obtaining an aqueous slurry in which 3,3 ′, 5,5′-tetraalkyl-4,4′-biphenol is dispersed in the aqueous reaction solution to be contained, and 3,3 ′, 5 from the obtained aqueous slurry , 5′-tetraalkyl-4,4′-biphenol comprising a step (B) of solid-liquid separation, and a method for producing 3,3 ′, 5,5′-tetraalkyl-4,4′-biphenol Then, a mixture containing water, unreacted 2,6-dialkylphenol and a 2-carbonylphenol compound represented by the following general formula (I) as impurities is distilled by rectification from the aqueous reaction solution recovered in step (B). Put out Recovery Te and 3,3 and supplying a part of the collected fractions to oxidative dimerization 'lies in the method for producing a 5,5'-tetraalkyl-4,4'-biphenol.

The third gist of the present invention is to carry out an oxidative dimerization reaction of 2,6-dialkylphenol with oxygen or an oxygen-containing gas in the presence of a water solvent and a metal catalyst, and to convert unreacted 2,6-dialkylphenol and the metal catalyst. A step (A) of obtaining an aqueous slurry in which 3,3 ′, 5,5′-tetraalkyl-4,4′-biphenol is dispersed in the aqueous reaction solution to be contained, and 3,3 ′, 5 from the obtained aqueous slurry , 5′-tetraalkyl-4,4′-biphenol comprising a step (B) of solid-liquid separation, and a method for producing 3,3 ′, 5,5′-tetraalkyl-4,4′-biphenol After the step (A) and before the step (B), the aqueous slurry is subjected to simple distillation, and water, unreacted 2,6-dialkylphenol and 2-carbonyl represented by the following general formula (I) as impurities With phenolic compounds Recovered by distillation a mixture containing, and, 2-carbonyl represented by step following formula from the aqueous reaction liquid recovered in (B) as a water and unreacted 2,6-dialkylphenols and impurity (I) phenolic compounds and the containing mixture is distilled by rectification is recovered, and supplying the oxidizing dimerization reaction portion of the recovered fraction obtained by the above two recovery steps 3,3 ', It resides in a process for producing 5,5′-tetraalkyl-4,4′-biphenol.

  In the method for producing a tetraalkylbiphenol of the present invention, even when unreacted dialkylphenol is recovered and reused repeatedly, a decrease in the conversion rate and an increase in the reaction time in the oxidation dimerization reaction are suppressed. This is an industrially advantageous production method capable of reducing the amount of unreacted dialkylphenol discarded, and the industrial value of the present invention is high.

  The present invention will be described in detail below. The production method of the present invention performs an oxidative dimerization reaction of 2,6-dialkylphenol with oxygen or an oxygen-containing gas in the presence of a water solvent and a metal catalyst, and mainly contains unreacted 2,6-dialkylphenol and a metal catalyst. A reaction step (A) for obtaining an aqueous slurry in which a tetraalkylbiphenol is dispersed in an aqueous reaction solution, and a step (B) for solid-liquid separation of the tetraalkylbiphenol from the obtained aqueous slurry. In addition, in order to help an understanding of this invention, one example of the flowchart corresponding to the 1st-3rd summary of this invention is shown in FIG. Hereinafter, the above-mentioned reaction step (A) is abbreviated as step (A).

  First, the step (A) will be described. Step (A) is an oxidation dimerization reaction step of 2,6-dialkylphenol. In the present invention, 2,6-dialkylphenol is an alkylphenol in which the 2,6-position of phenol is substituted with an alkyl group having 1 to 4 carbon atoms. Examples of the alkyl group having 1 to 4 carbon atoms include methyl group, ethyl group, n-propyl group, 1-propyl group, n-butyl group, 1-butyl group, s-butyl group, and t-butyl group. Of particular industrial importance is 2,6-dimethylphenol (2,6-xylenol) in which the alkyl group is a methyl group.

  Water is used as the reaction solvent, and the reaction is preferably carried out under alkaline conditions by adding an alkaline substance. Examples of the alkaline substance include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkali metal carbonates such as sodium carbonate, boron compounds such as hydrogen carbonate, sodium borate and borax, sodium phosphate and phosphoric acid. Examples include alkali metal phosphates such as sodium hydrogen, potassium phosphate and potassium hydrogen phosphate, and amine bases such as triethylamine and pyridine. Of these, boron compounds, particularly borax, are preferred from the viewpoint of yield and selectivity. The alkaline substance is usually used in such an amount that the pH of the reaction system is maintained in the range of 8-11. The amount of the alkaline aqueous solvent to be used is usually 100 to 1000 ml, preferably 100 to 500 ml, per mole of 2,6-dialkylphenol.

  A surfactant is preferably added to the reaction solvent, and specific examples thereof include fatty acid soaps, alkyl sulfonates, alkyl benzene sulfonic acids, alkyl sulfates, etc., preferably alkyl sulfates, among which lauryl sulfate. Sodium is preferred from the viewpoints of reaction rate and foamability. The amount of the surfactant used is usually 0.1 to 50 mmol per 1 mol of 2,6-dialkylphenol.

  As the metal catalyst, various transition metal compounds can be used, and among them, a copper compound is preferably used. The copper compound can be either monovalent or divalent, and examples thereof include copper halide, copper hydroxide, copper sulfate, copper nitrate, copper carboxylate, and copper alkyl sulfate. The usage-amount of a metal catalyst is 0.005-0.04 mmol normally per mol of 2, 6- dialkylphenol, Preferably it is 0.01-0.04 mmol.

  An oxygen-containing gas such as oxygen gas or air is used as an oxidizing agent in the oxidation dimerization reaction.

  The reaction temperature of the oxidation dimerization reaction is usually 50 to 100 ° C., and the reaction pressure is usually in the range of atmospheric pressure to 30 atmospheres depending on the oxygen concentration in the gas phase, and the reaction time is usually 5 to 15 hours. It is. The reaction is terminated by stopping the supply of oxygen gas or oxygen-containing gas.

  The resulting reaction solution was obtained by adding tetra-alkaline in an aqueous alkaline reaction solution containing unreacted 2,6-dialkylphenol, a surfactant, a metal catalyst and a 2-carbonylphenol compound represented by the above formula (I) by-produced as impurities. This is an aqueous slurry in which alkylbiphenol is dispersed.

  The 2-carbonylphenol compound is considered to be produced by oxidation of the alkyl chain of alkylphenols during the oxidative dimerization reaction. Specifically, salicylaldehydes, salicylic acids, 2- (alkylcarbonyl) -phenols are produced. It is kind. Since the 2-carbonylphenol compound is close in properties such as boiling point and solubility when the unreacted 2,6-dialkylphenol described later is recovered by distillation, it is in the recovered fraction of unreacted 2,6-dialkylphenol. It accumulates when it is mixed and collected repeatedly. If the 2-carbonylphenol compound is present in a large amount in the recovered fraction, the oxidative dimerization reaction of 2,6-dialkylphenol is inhibited when unreacted 2,6-dialkylphenol is recovered and reused. Among the 2-carbonylphenol compounds, salicylaldehydes are particularly easily produced and concentrated, and the oxidative dimerization reaction inhibition effect is great. For example, when 2,6-xylenol is used as a raw material, 3-methylsalicylaldehyde accumulates in the recovered fraction and greatly inhibits the oxidative dimerization reaction.

  The residual ratio of unreacted 2,6-dialkylphenol in the aqueous slurry after the oxidation dimerization reaction varies depending on the type of the alkyl group, but is generally in the range of 5 to 50% by weight, and particularly the residual ratio of 10 to 20% by weight. In this case, it is preferable from the viewpoint of the yield and selectivity of the tetraalkylbiphenol. The residual ratio of unreacted 2,6-dialkylphenol can be controlled by the amount of the oxidizing agent (oxygen) supplied.

  The aqueous slurry obtained in the step (A) may be supplied to the next solid-liquid separation step (B) as it is, but by performing the post-treatment described below before the solid-liquid separation, the high-purity can be efficiently obtained. Since tetraalkylbiphenol can be obtained, it is preferable.

  That is, after the oxidation dimerization reaction, the aqueous slurry obtained by stopping the supply of the oxygen-containing gas is preferably replaced with oxygen in the reactor by an inert gas such as nitrogen, and then an acid is added. Then, the pH of the aqueous slurry is adjusted so that the pH during the heat treatment performed is 7 or less, preferably in the range of 6-7. By this pH adjustment, an increase in heavy impurities such as polyphenylene ether by-produced during the heat treatment is prevented. The acid used for pH adjustment is not particularly limited, but generally a mineral acid is used, and sulfuric acid or hydrochloric acid is preferred.

  Next, heat treatment is performed. The heat treatment is usually performed at a temperature of 60 to 120 ° C. and normal pressure, and the treatment time is usually within 10 hours. By this heat treatment, diphenoquinones produced as a by-product in the reaction can be reduced, and the yield of tetraalkylbiphenol can be increased.

  Next, an acid is further added to the heat-treated aqueous slurry to adjust the pH of the reaction solution to preferably 2.5 to 5 (especially when the raw material 2,6-dialkylphenol is 2,6-xylenol, preferably 3-4. 5). The acid used for pH adjustment is not particularly limited, but generally a mineral acid is used, and sulfuric acid or hydrochloric acid is preferred. Adjusting the pH after the heat treatment is effective in preventing contamination of inorganic impurities such as metal catalysts in the product tetraalkylbiphenol.

  Alcohol is added to the aqueous slurry whose pH has been adjusted, and mixed and stirred. The amount of alcohol added is preferably such that the weight ratio of water / alcohol is 5/5 to 8/2. Particularly when 2,6-dialkylphenol as a raw material is 2,6-xylenol, It is preferable to add so that the weight ratio of / alcohol is 6/4 to 7/3. By adding alcohol, heavy impurities such as polyphenylene ether can be dissolved and removed from the aqueous slurry.

  As said alcohol, C1-C4 lower alcohols, such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, can be used conveniently. By setting the mixing ratio of water and alcohol within the above range, the solubility of the tetraalkylbiphenol can be reduced, the recovery rate can be maintained high, and the solubility of impurities to be removed can be maintained sufficiently high.

  The mixing and stirring after the addition of the alcohol is usually performed at a temperature of 40 to 100 ° C., preferably 50 to 90 ° C., usually for 0.1 to 5 hours, preferably 0.5 to 3 hours. The concentration of tetraalkylbiphenol in the mixed solution to which alcohol has been added is usually 5 to 50% by weight.

  Next, the solid-liquid separation step (B) will be described. Hereinafter, the solid-liquid separation step (B) is abbreviated as step (B). In the step (B), the product tetraalkylbiphenol is separated by solid-liquid separation of the aqueous or alcohol-containing aqueous slurry obtained through the step (A) or the additional step such as heat treatment. There is no particular limitation on the solid-liquid separation method, and usual means such as filtration and centrifugation can be used. The temperature of the slurry during solid-liquid separation is usually 35 to 70 ° C, preferably 40 to 65 ° C. If the temperature is too high, it is easy to remove organic impurities, but the product yield tends to decrease, and if the temperature is too low, the content of organic impurities in the tetraalkylbiphenol tends to increase.

  The solid phase containing a tetraalkylbiphenol obtained by solid-liquid separation usually contains 10 to 30% of liquid. This liquid component contains unreacted 2,6-dialkylphenol, reaction by-products such as heavy impurities, a surfactant, and the like. Moreover, when refine | purifying by alcohol washing | cleaning before performing a process (B), the alcohol used for washing | cleaning is contained. Therefore, it is usually preferable to further purify the product to obtain a high-purity product. As an additional purification method for obtaining a high-purity product, it is industrially simple and preferable to rinse and wash the solid phase after solid-liquid separation with warm water. The temperature of the warm water is usually 35 to 90 ° C, preferably 40 to 65 ° C. The amount of warm water is usually 0.5 to 3 times (weight ratio) with respect to the solid phase, although it depends on the temperature and the washing method. As another purification method, the solid phase after solid-liquid separation may be mixed and washed with warm water or an organic solvent, and solid-liquid separation may be performed again to separate the solid phase and the liquid phase.

  The aqueous reaction liquid recovered in the solid-liquid separation contains water, unreacted 2,6-dialkylphenol, a surfactant, a metal catalyst, and a 2-carbonylphenol compound represented by the above formula (I) as an impurity. In addition, when an additional step such as heat treatment and purification with an alcohol is performed before the step (B), the aqueous alkaline reaction solution contains an alcohol.

  In the production method described in the first aspect of the present invention, the aqueous slurry after the oxidation reaction is distilled, and is mainly composed of water and unreacted 2,6-dialkylphenol, and contains a 2-carbonylphenol compound as an impurity. The mixture is distilled, a part of the recovered fraction is supplied to the oxidation dimerization reaction, and reused as a part of the reaction raw material 2,6-dialkylphenol.

  The recovered fraction contains a 2-carbonylphenol compound (for example, when 2,6-dialkylphenol is 2,6-xylenol, the recovered fraction contains 3-methylsalicylaldehyde). By performing the above operation, accumulation of the 2-carbonylphenol compound in the oxidation dimerization reaction solution is suppressed (as compared to the case where the entire recovered fraction is always supplied to the oxidation dimerization reaction), It is possible to reduce the amount of 2,6-dialkylphenol, which is an unreacted raw material to be disposed of, and to reduce the amount of unreacted raw material to be discarded, while reducing the conversion rate in the oxidation dimerization reaction and increasing the reaction time. This is an advantageous production method.

  When distillation of the aqueous slurry is performed in combination with the above-described post-treatment step before solid-liquid separation, the pH of the aqueous slurry is usually adjusted to 7 or less, preferably 6 to 7, and then the heat treatment before adding the alcohol. It is preferred to distill and recover the unreacted xylenol by distilling the aqueous slurry simultaneously with the heating operation in the process.

  The temperature and pressure for distillation of the aqueous slurry may be selected under conditions in which water and 2,6-dialkylphenol are azeotroped, and distillation may be performed under pressure or under reduced pressure as necessary. For example, when 2,6-dialkylphenol is 2,6-xylenol, it may be distilled at normal pressure and about 100 ° C. The distillation method in the case of distilling the aqueous slurry obtained by performing the step (A) or the above-mentioned post-treatment may be simple distillation, but the rectification method increases the reflux ratio and concentrates and separates the 2-carbonylphenol compound. can do. In the case of distillation, when the concentration of the aqueous slurry becomes too high and operations such as stirring become difficult, distillation may be carried out while adding water or water vapor to the system.

  Various methods are conceivable as a method for supplying a part of the recovered fraction to the oxidation dimerization reaction. As a typical method, the entire amount of the recovered fraction is supplied several times to the oxidation dimerization reaction and then recovered. A method in which part or all of the fraction is removed and supplied to the oxidation dimerization reaction (that is, the recovered fraction is removed once for several reactions), and the recovered fraction in each distillation operation There is a method of removing a part and supplying to the oxidation dimerization reaction, and any method may be used. In the former method, the operation is simple, and in the latter method, the reaction results of each round are easily stabilized.

  When the recovered fraction is removed once for the former several reactions, the ratio of the recovered fraction supplied to the oxidation dimerization reaction varies greatly each time, but can be expressed as an average in a plurality of reaction cycles. . It is preferable to adopt the most efficient number of times and supply amount in consideration of the reaction time at each time, the concentration of the 2-carbonylphenol compound, and the amount of the recovered fraction not reused in the reaction.

  When a part of the recovered fraction is removed in the latter distillation operation, the ratio of the recovered fraction supplied to the oxidative dimerization reaction can be carried out almost stably each time. In this case as well, it is preferable to adopt the most efficient supply ratio in consideration of the reaction time, the concentration of the 2-carbonylphenol compound, and the waste amount of the recovered fraction not reused in the reaction.

  In any of the above methods, the ratio of the recovered fraction supplied to the oxidation dimerization reaction is usually based on the unreacted 2,6-dialkylphenol in the recovered fraction, although it depends on the distillation recovery conditions. 99% by weight or less, preferably 50 to 99% by weight, and more preferably 90 to 99% by weight (when the recovered fraction is removed once for several reactions, the average feed rate of each time is used). When the proportion of the recovered fraction supplied to the oxidation dimerization reaction is too large, the amount of unreacted raw material 2,6-dialkylphenol to be discarded is further reduced, but the 2-carbonylphenol compound is used for the oxidation dimerization reaction. It accumulates, the conversion rate in the oxidation dimerization reaction decreases, and the reaction time increases. On the other hand, when the proportion of the recovered fraction supplied to the oxidative dimerization reaction is too small, the effect of suppressing the accumulation of 2-carbonylphenol compound in the oxidative dimerization reaction and the reduction in conversion rate and reaction time in the oxidative dimerization reaction The effect of suppressing the increase in the amount is saturated, and the amount of unreacted raw material 2,6-dialkylphenol to be discarded increases, which is economically disadvantageous.

  When distillation recovery is performed by simple distillation, the concentration of impurities in the 2,6-dialkylphenol in the recovered fraction tends to increase, so the proportion of the recovered fraction supplied to the oxidation dimerization reaction needs to be relatively low. The amount is usually 95% by weight or less, preferably 50 to 90% by weight. In addition, when the distillation recovery is performed by precision distillation, since the recovered fraction excluding the fraction enriched with the impurity 2-carbonylphenol compound can be supplied to the oxidation dimerization reaction, the recovery fraction that is not supplied to the oxidation dimerization reaction. The weight of the part (remainder) can be reduced to a small amount (usually 1/5 to 1/10) compared to the remainder when the recovery is performed by simple distillation, that is, the recovery supplied to the oxidation dimerization reaction. It is possible to increase the fraction. After the concentration and separation, a part of the unreacted raw material 2,6-dialkylphenol may be further supplied to the oxidation dimerization reaction from the remainder.

  The concentration of the 2-carbonylphenol compound in the recovered 2,6-dialkylphenol of the unreacted raw material is preferably less than 5% by weight, more preferably less than 2% by weight. The recovered unreacted raw material 2,6-dialkylphenol is supplied to the oxidation dimerization reaction together with the new raw material 2,6-dialkylphenol. The concentration of the 2-carbonylphenol compound contained in the 2,6-dialkylphenol in the charged reaction solution is preferably less than 0.5% by weight, more preferably less than 0.2% by weight.

  In the production method described in the second aspect of the present invention, the aqueous reaction liquid recovered in the step (B) is distilled, and is mainly composed of water and unreacted 2,6-dialkylphenol. A mixture containing a phenol compound is distilled, a part of the recovered fraction is supplied to the oxidation dimerization reaction, and reused as a part of the reaction raw material 2,6-dialkylphenol. By this operation, an effect similar to the effect described in the first gist is obtained, and an industrially advantageous production method is obtained.

  When the post-treatment step described above is performed after step (A), the aqueous reaction solution contains a lower alcohol or the like. In this case, a 2,6-dialkylphenol is recovered after removing low-boiling compounds such as lower alcohol in the distillation step. In addition, when an aqueous reaction liquid is acidic, it is preferable to neutralize an aqueous reaction liquid using alkalis, such as sodium hydroxide, before heating by distillation from points, such as corrosion prevention of an apparatus.

  The temperature and pressure for distillation of the aqueous reaction solution may be selected under conditions where water and 2,6-dialkylphenol are azeotroped, and may be distilled under pressure or reduced pressure as necessary. The distillation method may be simple distillation, but the rectification method is particularly preferred when the aqueous reaction solution contains lower alcohol or the like. By adopting the rectification method, not only can the alcohol be recovered and reused, but also the reflux ratio can be increased and the 2-carbonylphenol compound can be concentrated and separated. In the case of distillation, when the concentration of the aqueous slurry becomes too high and operations such as stirring become difficult, distillation may be carried out while adding water or water vapor to the system.

  The method of supplying a part of the recovered fraction to the oxidation dimerization reaction is the same as that described in the first gist.

  The ratio of the recovered fraction supplied to the oxidation dimerization reaction is the same as that described in the first aspect.

  The preferred concentration of the 2-carbonyl compound in the recovered unreacted raw material 2,6-dialkylphenol and in the charged reaction solution is the same as that described in the first aspect.

  In the third aspect of the present invention, the aqueous reaction liquid recovered in the distillation recovery operation (pre-stage distillation step) from the aqueous slurry explained in the first summary and the step (B) explained in the second summary. And a distillation recovery operation (second-stage distillation step) from the above. The distillation recovery method for each recovery operation can be performed in the same manner as described in the first and second aspects. By this operation, an effect similar to the effect described in the first gist is obtained, and an industrially advantageous production method is obtained.

  As described in the gist of the first and second inventions, the operations in the pre-stage distillation process and the post-stage distillation process can be carried out by simple distillation or precision distillation, but precision distillation has fewer impurities. This is preferable because unreacted raw materials can be recovered. However, since the 2-carbonylphenol compound tends to be concentrated in the latter-stage distillation, the first-stage distillation step can be carried out without any disadvantage even with simple simple distillation. As for the post-stage distillation step, simple distillation is also possible. However, when the aqueous slurry contains a lower alcohol, precision distillation is preferable in order to separate it and concentrate and separate the 2-carbonylphenol compound.

  As a method for supplying the recovered fraction obtained in the preceding distillation step and the subsequent distillation step to the oxidation dimerization reaction, the following method can be employed. (1) A method in which the recovered fractions obtained in both steps are collected and a part thereof is supplied to the reaction solution. (2) A method in which the recovered fraction obtained in both steps is independently supplied to the reaction. In the case of the method of (2), there is a degree of freedom in the supply ratio of the recovered fractions of both steps to the oxidation dimerization reaction, and it is possible to supply one fraction all and partly supply one fraction. Part of both fractions can also be supplied.

  The ratio of supplying the recovered fractions obtained in the former distillation step and the latter distillation step to the oxidation dimerization reaction depends on the distillation recovery method, but is based on the unreacted 2,6-dialkylphenol in the entire recovered fraction. Usually, it is 99 weight% or less, Preferably it is 50 to 99 weight%, More preferably, it is 90 to 99 weight%. Especially when the 2-carbonylphenol compound is concentrated and recovered during precision distillation in the latter stage distillation process, the recovered fraction excluding the concentrated fraction is supplied to the oxidation dimerization reaction to increase the supply ratio. I can do it.

  The manufacturing method according to the third aspect of the present invention can be said to be an industrially very efficient manufacturing method. For example, before the step (B), the aqueous slurry is heated and purified, and the unreacted 2,6-dialkylphenol is recovered by distillation using the heat treatment to some extent before the step (B). If the method of distilling and recovering the unreacted 2,6-dialkylphenol and distilling and recovering the remaining unreacted 2,6-dialkylphenol from the aqueous reaction liquid recovered in the step (B) is adopted, the step (B) Compared to the case where the distillation recovery is performed only before or after the step (B), the load in the distillation is reduced, the distillation recovery time is shortened, and an appropriate slurry concentration is obtained during the distillation of the aqueous slurry. It has the advantage that it can be maintained. Moreover, the amount of the aqueous slurry to be used in the step (B) is reduced, the load on the solid-liquid separation step is reduced, and the production time can be shortened.

  As an example of a particularly preferable production method, after the oxidation dimerization reaction in the step (A), the pH of the aqueous slurry is adjusted to 7 or less, and heat treatment is performed, and at the same time, the recovery of 2,6-dialkylphenol by the previous distillation step After the lower alcohol was mixed with the pH being acidic, the solid-liquid separation step of step (B) was performed, and the pH of the aqueous reaction solution obtained was further adjusted to 7 or higher, and then 2 in the subsequent distillation step. , 6-dialkylphenol can be recovered, and a part of 2,6-dialkylphenol recovered in the former distillation step and the latter distillation step can be reused in the oxidative dimerization reaction.

  The ratio of the amount of unreacted 2,6-dialkylphenol recovered in the first distillation step and the amount of unreacted 2,6-dialkylphenol recovered in the second distillation step should be selected so that the production efficiency is optimal. Good. When the total amount of unreacted 2,6-dialkylphenol to be recovered by distillation is 100 parts by weight, the amount of unreacted 2,6-dialkylphenol to be recovered in the previous distillation step is usually 20 parts by weight or more, preferably 30 to 50% by weight. The amount of unreacted 2,6-dialkylphenol recovered in the subsequent distillation step is usually 80 parts by weight or less, preferably 70 to 50 parts by weight.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to a following example. In addition, the analysis method of 2, 6- xylenol and 3-methyl salicyl aldehyde (MSA) in an Example and a comparative example is shown below.

For quantitative analysis of 2,6-xylenol and MSA, a phenylmethylsilicone capillary column (J & W “CBP-5”) having a crosslinking degree of 5% is used as a column, and a flame ionization detector (FID) is used as a detector. A gas chromatograph (“GC-14B” manufactured by Shimadzu Corporation) was used. A measurement sample was prepared by dissolving 20 g of a sample in 20 ml of dimethylformamide, and phenol was used as an internal standard substance. 2,6-xylenol was quantified by the internal standard method, and MSA was determined based on the purity of 2,6-xylenol quantified by the internal standard method and the area ratio of the gas chromatograph chart of 2,6-xylenol and MSA. Calculated.

Example 1:
A stainless steel reactor was fed with 100 parts by weight of a distilled and recovered liquid containing 11% by weight of 2,6-xylenol (consisting of 11 parts by weight of 2,6-xylenol and 89 parts by weight of water) from the recovered raw material tank, and subsequently 64 parts by weight of new raw material 2,6-xylenol and 42 parts by weight of new water were added, and the temperature was raised while stirring. The concentration of MSA contained in 2,6-xylenol in the charged reaction solution was 0.07% by weight. When the temperature of the contents reached 60 ° C., 3.3 parts by weight of borax, 0.13 parts by weight of sodium lauryl sulfate and 0.004 parts by weight of cupric acetate were added, and the temperature was raised while stirring. . When the temperature of the contents reached 70 ° C., introduction of oxygen was started. Stirring was continued so that the reaction temperature was maintained at 70 ° C., and the introduction of oxygen was stopped when oxygen was consumed in an amount to oxidize and dimerize about 85% by weight of the raw material 2,6-xylenol. Was purged with nitrogen.

  Next, 98 wt% sulfuric acid was added to adjust the pH of the resulting aqueous slurry to 6.2, and then the temperature was gradually raised and simple distillation was carried out to remove 8 parts by weight of the first fraction containing light boiling components out of the system. Thereafter, 28 parts by weight of a mixture comprising water and unreacted 2,6-xylenol was distilled off and recovered in a recovery raw material tank. Thereafter, the temperature in the reactor was cooled from about 100 ° C. during simple distillation to 70 ° C., 98 wt% sulfuric acid was added to adjust the pH of the reaction solution to 3.7, and then isopropyl alcohol / water (86/14 (Wt%)) 87 parts by weight of a mixed solvent was added, and the mixture was stirred for 30 minutes while adjusting the temperature in the reactor to 60 ° C.

  Next, while maintaining the temperature of the aqueous slurry at 60 ° C., the aqueous slurry is solid-liquid separated using a batch-type centrifugal filter, and the solid in the centrifuge is removed using 59 parts by weight of 60 ° C. hot water. Washing gave 57 parts by weight of 3,3 ′, 5,5′-tetramethyl-4,4′-biphenol containing 16% by weight of water.

  A 48% by weight aqueous caustic soda solution was added to the aqueous reaction solution recovered from the centrifugal filter to adjust the pH to 7-8, and then the temperature was gradually raised and precision distillation (rectification) was performed. After recovering the mixture fraction containing isopropyl alcohol and water at about 80 ° C., the temperature was further raised and the rectification was continued while maintaining the reflux ratio at about 1. 72 parts by weight of a mixture containing 2,6-xylenol was distilled and recovered in the above-described recovery raw material tank.

  When the above operation was repeated a total of 4 times, the reaction time required to consume a predetermined amount of oxygen increased from 12 hours to 13.8 hours, and the 2,6-xylenol in the charged reaction liquid was increased. The concentration of MSA contained increased to 0.13% by weight. Next, for the fifth operation, 50% by weight (50 parts by weight) of the distilled and recovered liquid in the recovered raw material tank is removed from the system, and the remaining 50% by weight (50 parts by weight) is supplied to the reaction tank for reuse. did. At this time, since 5.5 parts by weight of the recovered raw material 2,6-xylenol and 44.5 parts by weight of water were reduced, 69.5 parts by weight of new raw material 2,6-xylenol and 86.5 parts by weight of new water were obtained. Was added. The reaction time in the fifth operation was shortened to 11.6 hours, and the concentration of MSA in 2,6-xylenol in the charged reaction solution was 0.06% by weight. Table 1 shows the transition of the supply ratio of the recovered fraction, the reaction time, and the concentration of MSA contained in 2,6-xylenol in the charged reaction liquid in the above five operations. Since 2,6-xylenol recovered through 5 operations was 55 parts by weight (11 parts by weight × 5 times) and discarded 2,6-xylenol was 5.5 parts by weight, The average feed rate of xylenol was 90% by weight.

Example 2:
By the same operation as in Example 1, the collection and reuse of unreacted 2,6-xylenol was repeated a total of 7 times. During this time, the concentration of MSA in 2,6-xylenol in the reaction charge increased from 0.08% to 0.13% by weight, and the reaction time required to consume a certain amount of oxygen. Increased from 12 hours to 14.9 hours. Then, in the eighth operation, when the aqueous reaction solution recovered from the centrifugal filter is distilled, the pH is adjusted to 7 to 8 by adding 48% by weight aqueous caustic soda solution at about 80 ° C. After recovering a mixture fraction containing isopropyl alcohol and water, rectification was carried out while further raising the temperature and maintaining the reflux ratio at about 6.

  First, 49 parts by weight of the fraction (1) containing mainly MSA and 2,6-xylenol was reduced, and then 23 parts by weight of the fraction (2) containing MSA-enriched water and xylenol was collected. . The fraction (1) contains 42.2 parts by weight of water and 6.8 parts by weight of 2,6-xylenol, and MSA is contained by 0.1% by weight with respect to 2,6-xylenol. It was collected in a tank. The fraction (2) contained 21.9 parts by weight of water and 1.1 parts by weight of 2,6-xylenol, and MSA was contained by 4% by weight based on 2,6-xylenol. The recovered fraction in the recovered raw material tank (consisting of 9.9 parts by weight of xylenol and 67.1 parts by weight of water) is reused for the oxidation dimerization reaction, and the recovered fraction (2) in which MSA is concentrated (recovered fraction) Containing 10% by weight of 2,6-xylenol and 65% by weight of MSA) was not reused. At this time, 1.1 parts by weight of the recovered raw material 2,6-xylenol and 21.9 parts by weight of water were reduced, so 65.1 parts by weight of new raw material 2,6-xylenol and 63.9 parts by weight of water were added. did.

  In the eighth reaction operation, the concentration of MSA in 2.6-xylenol of the reaction charge was 0.05% by weight, and the reaction time was reduced to 11.7 hours. Table 1 shows the supply ratio of the recovered fraction, the reaction time, and the transition of the concentration of MSA contained in 2,6-xylenol in the reaction charge in the above eight operations. Through these eight operations, 2,6-xylenol supplied to the oxidation dimerization reaction was 86.9 parts by weight with respect to 88 parts of 2,6-xylenol in the recovered fraction containing fraction (2). The proportion was 98.8% by weight.

Comparative Example 1:
In Example 1, the operation of reusing the entire amount of unreacted 2,6-xylenol collected by distillation was repeated 13 times. In the fifth operation of recovery and reuse, the reaction time required to consume a predetermined amount of oxygen increased from 12.7 hours to 14 hours, and in 2,6-xylenol in the reaction solution. The concentration of MSA increased from 0.09 wt% to 0.13 wt%. Furthermore, when the collection and reuse were repeated, the reaction time required to consume a predetermined amount of oxygen in the 13th operation of the collection and reuse increased to 17.3 hours. The concentration of MSA in 2,6-xylenol increased to 0.25 wt%. The average reaction time became longer and the productivity per unit time deteriorated. Table 1 shows the transition of the supply ratio of the recovered fraction, the reaction time, and the concentration of MSA contained in 2,6-xylenol of the charged reaction liquid in the 13 operations described above.

1 is an example of a flow chart showing a manufacturing method of the present invention, and (1), (2), and (3) in the figure show the manufacturing methods according to the first, second, and third aspects of the present invention, respectively. It is an example of a flow diagram.

Claims (7)

In the presence of a water solvent and a metal catalyst, an oxidative dimerization reaction of 2,6-dialkylphenol is carried out with oxygen or an oxygen-containing gas, and an aqueous reaction solution containing unreacted 2,6-dialkylphenol and a metal catalyst is subjected to 3, 3 Step (A) for obtaining an aqueous slurry in which ', 5,5'-tetraalkyl-4,4'-biphenol is dispersed, and 3,3', 5,5'-tetraalkyl-4, A process for producing 3,3 ′, 5,5′-tetraalkyl-4,4′-biphenol comprising the step (B) of solid-liquid separation of 4′-biphenol, which is a step after step (A) before reaching (B), the perform distillation of an aqueous slurry by rectification method, containing a 2-carbonyl phenol compound represented by the following general formula (I) as a water and unreacted 2,6-dialkyl phenol and impurities A 3,3 ′, 5,5′-tetraalkyl-4,4′-biphenol, which is obtained by distilling and recovering the compound, and supplying a part of the recovered fraction to the oxidative dimerization reaction Production method.
In the presence of a water solvent and a metal catalyst, an oxidative dimerization reaction of 2,6-dialkylphenol is carried out with oxygen or an oxygen-containing gas, and an aqueous reaction solution containing unreacted 2,6-dialkylphenol and a metal catalyst is subjected to 3, 3 Step (A) for obtaining an aqueous slurry in which ', 5,5'-tetraalkyl-4,4'-biphenol is dispersed, and 3,3', 5,5'-tetraalkyl-4, A process for producing 3,3 ′, 5,5′-tetraalkyl-4,4′-biphenol comprising the step (B) of solid-liquid separation of 4′-biphenol, which is recovered in step (B) the mixture containing the 2-carbonyl phenol compound represented by the following general formula (I) from the aqueous reaction mixture as water and unreacted 2,6-dialkylphenol and impurities distilled off by rectification recovered, the recovered distillate 3,3 ', 5,5'-tetraalkyl-4,4'-biphenol method for manufacturing a part and supplying the oxidizing dimerization of.
In the presence of a water solvent and a metal catalyst, an oxidative dimerization reaction of 2,6-dialkylphenol is carried out with oxygen or an oxygen-containing gas, and an aqueous reaction solution containing unreacted 2,6-dialkylphenol and a metal catalyst is subjected to 3, 3 Step (A) for obtaining an aqueous slurry in which ', 5,5'-tetraalkyl-4,4'-biphenol is dispersed, and 3,3', 5,5'-tetraalkyl-4, A process for producing 3,3 ′, 5,5′-tetraalkyl-4,4′-biphenol comprising the step (B) of solid-liquid separation of 4′-biphenol, which is a step after step (A) Before reaching (B), simple distillation of the aqueous slurry is carried out, and a mixture containing water, unreacted 2,6-dialkylphenol and a 2-carbonylphenol compound represented by the following general formula (I) as impurities is distilled. out And water, unreacted 2,6-dialkylphenol, and 2-carbonylphenol compound represented by the following general formula (I) as impurities from the aqueous reaction solution recovered in step (B). 3,3 ′, 5,5′-tetra, characterized in that the mixture is recovered by distilling and recovered, and a part of the recovered fraction obtained in the above two recovery steps is supplied to the oxidation dimerization reaction. A method for producing alkyl-4,4′-biphenol.
The production method according to any one of claims 1 to 3, wherein 50 to 99% by weight of unreacted 2,6- dialkylphenol obtained as a recovered fraction is supplied to the oxidation dimerization reaction.   2,6-dialkylphenol is 2,6-xylenol, and 3,3 ′, 5,5′-tetraalkyl-4,4′-biphenol is 3,3 ′, 5,5′-tetramethyl-4, It is 4'-biphenol, The manufacturing method in any one of Claims 1-4.   6. The production according to claim 1, wherein the distillation of the aqueous slurry is performed simultaneously with the heat treatment after the step (A) by adding an acid to the aqueous slurry to adjust the pH to 7 or less. Method. A method in which a part of the recovered fraction is supplied to the oxidation dimerization reaction, a method in which the entire recovered fraction is supplied several times to the oxidation dimerization reaction and then the entire recovered fraction is removed, and an oxidation dimerization reaction. After supplying the entire amount of the recovered fraction several times, a part of the recovered fraction is removed and the remainder is supplied to the oxidation dimerization reaction, or a part of the recovered fraction is removed in each distillation operation. The production method according to claim 1, wherein the remainder is supplied to the oxidation dimerization reaction.